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Seeking critique of my formula and methods
Hi everyone,
I’m a beginner formulator who has spent a few months developing and testing this liquid shower gel formula. While I’m not a professional, I’ve done my best to conduct stability tests at home. I’m eager to improve and eventually sell my product, so I would greatly appreciate any input from professionals on this site. Thank you for taking the time to help!
Liquid Shower Gel Formula
- 8% Sodium Coco Sulfate
- 8% Cocomidopropyl Betaine
- 4% Coco-glucoside
- 2% Glycol Stearate
- 1% Essential Oil
- 0.8% Fragrance
- 14% Polysorbate 20
- 1.5% Niacinamide
- 53.5% Water
- 1.5% Optiphen Plus
- 5% Glycerin
- 0.7% Xanthan Gum
Some Issues:
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Surfactant and Emulsifier Ratios: I’ve used a 1:10 ratio of Polysorbate 20 for essential oil and a 1:5 ratio for fragrance oil. Is this excessive? (My essential oil dissolved in water with 1:1 ratio, but I just wanted to be sure.)
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Preservative Usage: My supplier recommended 0.5 to 1.5% Optiphen Plus for preservation. I opted for 1.5% to ensure effectiveness, but how do I determine the correct amount for a 2-year shelf life?
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Stability Concerns: I conducted stability tests on my sample. While there was no separation at cold or room temperatures, heated conditions led to the appearance of white particles and a thin layer of translucent liquid at the bottom within one week. What might be causing this issue?
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Please feel free to leave your comments on anything I might be doing wrong as well.
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3 Replies
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I see a few problems with your formula.
1. You include too much essential oil. The whole purpose of a shower gel is to REMOVE oil. When you put oil in your formula you cause two problems. First, you reduce the amount of surfactant available to clean the surface. Second, the essential oil is already tied up in a micelle and will just rinse down the drain. It is a complete waste of resources to include an essential oil, especially since you already have a fragrance! There are only two reasons to include an essential oil in a cleansing product. You need it for the odor or you want to tell a marketing story. If it’s a marketing story, you only need to add like 0.1%.
2. If your home stability test did not involve a Preservative Efficacy test then you haven’t really done a stability test.
3. Determining the correct amount for a 2-year shelf life is done just how you’re doing it. Use the highest amount you can safely add. Then when you find that is effective you can try to optimize the formula by using less. Of course, for that preservative you also need to keep the pH near or below 5.0 since Sorbic acid is one of the ingredients.
4. Niacinamide is water soluble. It is simply rinsing down the drain and doing nothing in your formula. Using it at 1.5% is just a waste of money. In a rinse-off cleanser, it is what is known as a “claims” ingredient. You put a tiny amount in there to get consumers to buy the product. It doesn’t have any effect on the skin.
The separation is most likely caused by the essential oil separating. Reduce the level since it is a pointless ingredient anyway.
Finally, if you are going to sell the product you need to have it stability tested by an independent lab. Home stability testing is just not appropriate for a commercial product.
Hope that helps!
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Xanthan gum does not give the best sensorials but for beginners it may be fine to work with. I would lower it to 0.5%. Preferably, I keep it at a max of 0.3% in creams but that will not be enough as a single thickener. Be advised that for larger batches, you will need to solvate the Xanthan gum into the water before adding your surfactants. Otherwise you will tend to create frothing and bubble formation that is difficult to dissipate. Glycerin is ridiculous addition to a body wash or shampoo. 5% is way too high. Use only what is needed to create a slurry with xanthan gum. Again, ideally you would not use xanthan gum as a thickener. As far as coco glucoside, I would advise substituting for Lamesoft PO65 which is a combination of Coco glucoside and Glyceryl Oleate, a refattening agent. It also has the tendency to thicken a surfactant system. Use 1.5-1.75%
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The amount of fragrance and essential oil is very high. Usually the combined total of fragrance and essential oil would be around 0.5% but maybe up to 1% depending on the fragrance/essential oil combination used.
Unless it is a particularly difficult to solubilise fragrance(or essential oil) you usually don’t need an additional solubiliser (i.e. Polysorbate 20) because the other surfactants solubilise the fragrance.
Try reducing the fragrance/essential oil and remove or lower the polysorbate 20. Remove or significantly reduce the glycerin. Doing the above will help to thicken the product and you should be able to reduce or remove the xanthan gum. Sodium coco sulfate should thicken with salt and this would give better sensorials than high amounts of xanthan gum.
Hope this helps 🙂
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